Invasion History

First Non-native North American Tidal Record: 1933
First Non-native West Coast Tidal Record:
First Non-native East/Gulf Coast Tidal Record: 1933

General Invasion History:

Argulus japonicus was described from Japan by Thiele in 1900, as a parasite of Goldfish (Carassius auratus) (Meehan 1940). Subsequently, it has been found on goldfish and other cyprinids around the world, including Britain (Rushton-Mellor 1992), South Africa (Shafir and Oldewage 1992), Sri Lanka, Israel, New Zealand (Hoffman and Schubert 1984), and North America (Cressey 1978). It is likely that this parasite was spread throughout much of its present range long before its description.

In North America, we know of only one record from tidal waters, in Chesapeake Bay, but it is likely that this parasite is established in other North American estuaries. In fish parasite surveys, fish-lice are often just identified as 'Argulus sp.'

The first record of A. japonicus in North America is an occurrence in Macon, Georgia (as A. trilineata) (Wilson 1902; Meehan 1940). Its spread in North America is not well-documented. United States National Museum of Natural History collections include aquarium, fishpond, and 'wild' specimens from Maryland and Virginia (from 1933-37), New York (from 1937), Massachusetts (from 1940), Michigan, (from 1974), Wisconsin (from 1988), and Puerto Rico (from 1991). However, Meehan (1940) noted that 'the species has been reported from almost every region where the goldfish Carassius auratus are found'. It is considered a commonly occurring pest in C. auratus and Cyprinus carpio (ornamental carp, koi) ponds (Hoffman 1977; Rushton-Mellor 1992). While it seems to be usually associated with these species in North America, it did not discriminate between C. carpio and the North American cyprinid Pimephales promelas (LaMarre and Cochran 1992). In the Great Lakes system, A. japonicus was collected from Michigan waters of Lake Erie in 1974 (US National Museum of Natural History 2012), and from the Fox River, Wisconsin which flows into Green Bay, Lake Michigan in 1988 (US National Museum of Natural History 2012; LaMarre and Cochran 1992). It has been reported from the Suwannee River, Florida (Mason et al. 1994).

North American Invasion History:

Invasion History on the East Coast:

Argulus japonicus was collected from Chesapeake Bay at Weems, Virginia, on the middle portion of the Rappahannock estuary, 'swimming freely in the tow', in 1933 (USNM 78895, US National Museum of Natural History 2012).


The fish lice of the subclass Branchiura are considered allied to the subclass Copepoda, and often lumped with parasitic copepods in ecological and fish-pathology discussions. However, they are morphologically distinct, and have some unique life history features (Barnes 1983).

Branchiurans have a large shield-like carapace, four pairs of thoracic legs, and a small, bilobed abdomen without terminal setae. Both the antennule and the antenna are small – the antenna has a large claw for attachment to the host. The mandibles are modified to form a sucking tube. In Argulus japonicus, there are no spines or scales at the base of the tube. Posterior to the eyes and antenna is a large pair of suckers, modified from the 2nd maxillae – these also function in attachment to the host. The outer rim of the sucker is composed of radiating rods, each comprised of multiple vertebra-like elements. Posterior to the suckers, and above the maxilla, thoracic legs are found on each side, visible as outlines in ventral view. Description based on Barnes 1983 and Thorp and Covich 2001.

Adult females of A. japonicus have a circular carapace, reaching posteriorly behind the 4th thoracic legs. The rami of the first three pairs of legs, and all but the 4th pair, are visible in a dorsal view. The abdomen is elliptical and narrows where it joins the thorax. There are 6-9 elements in the rods surrounding the sucker disk. In A. japonicus, the small respiratory area is anterior to the large respiratory area, which is kidney-shaped. The female is about 6 mm long. The male is considerably smaller than the female, with a smaller carapace, just reaching the abdomen. The testes are elongated ovals and extend into the abdominal lobes. Description based on Wilson 1944 and Cressey 1978. The larval stages of A. japonicus are described by Tokioka (1936).


Taxonomic Tree

Kingdom:   Animalia
Phylum:   Arthropoda
Subphylum:   Crustacea
Class:   Maxillopoda
Subclass:   Branchiura
Order:   Arguloida
Family:   Argulidae
Genus:   Argulus
Species:   japonicus


Argulus trilineatus (None, None)

Potentially Misidentified Species

Argulus catastomi
Found on fishes of the families Cyprinidae and Catastomidae in North America (Cressey 1978).



Adult Argulus spp. (Fish-Lice) are ectoparasites of fishes, which after a non-feeding nauplius stage, attach temporarily to a host and feed on its blood and mucus. They are capable of detaching and swimming from one fish to another, so they can be considered both zooplankters and parasites. The sexes are separate, and males are morphologically distinct. Copulation takes place on the host fish, but the eggs are laid on a hard substratum (Wilson 1902; Hoffman 1977; Cressey 1978; Barnes 1983).

The eggs hatch into a swimming nauplius which attaches itself to a fish. This molts into a juvenile stage, which has the basic features of the adult, but with incomplete development of the appendages and feeding stuctures. The juvenile goes through 6 molts to become an adult, while feeding on fish hosts. Remains of red blood cells were not found in juveniles, but adults were definitely feeding on the blood of Cyprinus carpio (Walker et al. 2011). Adults take at least 22 days to mature (at an unspecified temperature) (Tokioka 1936). They reproduce successfully at 10 to 35ºC (Shafir and Oldewage 1992). Salinity tolerance of A. japonicus is unknown - the one Chesapeake record was from the Rappahannock region which is usually mesohaline (5-18 PSU). Argulus japonicus is best known as a an ectoparasite of Goldfish (Carassius auratus) and Common Carp (Cyprinus carpio), but has been found on a variety of North American fishes, including Pimephales promelas (Fathead Minnow) and Dorosoma cepedianum (Gizzard Shad) (Cressey 1978; LaMarre and Cochran 1992; Poly 1998).


Fishes (blood)

Trophic Status:




General HabitatNontidal FreshwaterNone
General HabitatFresh (nontidal) MarshNone
General HabitatGrass BedNone
General HabitatCoarse Woody DebrisNone
General HabitatSwampNone
General HabitatUnstructured BottomNone
Salinity RangeLimnetic0-0.5 PSU
Salinity RangeOligohaline0.5-5 PSU
Tidal RangeSubtidalNone
Vertical HabitatPlanktonicNone
Vertical HabitatNektonicNone

Tolerances and Life History Parameters

Maximum Temperature (ºC)35None
Minimum Salinity (‰)0None
Maximum Reproductive Temperature15None
Broad Temperature RangeNoneCold temperate-Tropical
Broad Salinity RangeNoneNontidal Limnetic-Tidal Limnetic

General Impacts

Argulus japonicus is apparently present in natural waters in much of North America (Cressey 1978; LaMarre and Cochran 1992), but its effects on wild fish populations are unknown. Argulus japonicus can be a serious pest in aquaculture, including rearing of cyprinid fishes for food, baitfish rearing, and ornamental culture of Goldfish (Carassius auratus) and Common Carp (Cyprinus carpio) (Hoffman 1977; Rushton-Mellor 1992; Jafri and Ahmed 1994). In some parts of the world, including South Africa, it has become an abundant parasite of native cyprinid fishes (Shafir and Oldewage 1992), but its impacts on fisheries have apparently not been quantified.

Regional Distribution Map

Bioregion Region Name Year Invasion Status Population Status
M130 Chesapeake Bay 1933 Def Estab
GL-II Lake Erie 1974 Def Estab
G080 Suwannee River 1994 Def Estab
L042 _CDA_L042 (Fox River) 1988 Def Estab
L085 _CDA_L085 (Detroit) 1974 Def Estab

Occurrence Map

OCC_ID Author Year Date Locality Status Latitude Longitude


Barnes, Robert D. (1983) Invertebrate Zoology, Saunders, Philadelphia. Pp. 883

Basten, Douglas J., Cochran, Philip A. (1991) Effect of a fish medication on Argulus japonicus, a crustacean parasite of fish, Journal of Freshwater Ecology 6(4): 457-458

Cressey, Roger F. (1978) Marine flora and fauna of the northeastern United States. Crustacea: Branchiura, NOAA Technical Report Circular 413: 1-9

Glarowicz, Tracy, Cochran, Philip A. (1991) Response by the parasitic crustacean Argulus japonicus to host chemical cues, Journal of Freshwater Ecology 6(4): 455-456

Hoffman, Glenn L. (1967) Parasites of North American freshwater fishes, In: (Eds.) . , Berkeley. Pp. <missing location>

Hoffman, Glenn L. (1977) Argulus, a Branchiuran parasite of freshwater fishes, United States Fish and Wildlife Service Fish Disease Leaflet 49: 1-9

Hoffman, Glenn, L.; Schubert, Gottfried (1984) Distribution, Biology, and Management of Exotic Fishes., Johns Hopkins University Press, Baltimore, MD. Pp. 233-261

Jafri, S. I. H.; Ahmed, S. S. (1994) Some observations on mortality in major carps due to fish lice and their chemical control, Pakistan Journal of Zoology 26(3): 274-276

Kennedy, C. R. (1993) Introductions, spread, and colonization of new localities by fish helminth and crustacean parasites in the British Isles: A perspective and appraisal, Journal of Fish Biology 43: 287-301

LaMarre, Ellen; Cochran, Philip A. (1992) Lack of host species selection by the exotic parasitic crustacean, Argulus japonicus., Journal of Freshwater Ecology 7(1): 77-80

Mason, William T., Jr., Mattson, Robert A., Epler, John H. (1994) Benthic invertebrates and allied macrofauna in the Suwannee River and estuary ecosystem, Florida, Florida Scientist 57(4): 141-160

Meehan, O. Lloyd (1940) A review of the parasitic Crustacea of the genus Argulus in the collections of the United States National Museum, Proceedings of the United States National Museum 88(3087): 459-521

Poly, William J. (1998) New state, host, and distribution records of the fish ectoparasite, Argulus (Branchiura), from Illinois (U.S.A.), Crustaceana 71(1): 1-8

Reid, Janet L.; Hudson, Patrick (2008) Comment on 'Rate of species introductions in the Great Lakes via ships' ballast water and sediments', Canadian Journal of Fisheries and Aquatic Science 65: 549-553

Rushton-Mellor, S. K. (1992) Discovery of the fish louse Argulus japonicus (Crustacea:Branchiura) in Britain., Aquaculture and Fisheries Management 23: 269-271

Shafir, A.; Oldewage, W. H. (1992) Dynamics of a fish ectoparasite population: Opportunistic parasitism in Argulus japonicus., Crustacean 62(1): 50-64

Thorp, James H.; Covich, Alan P. (2001) <missing title>, Academic Press, San Diego CA. Pp. <missing location>

Tokioka, Takasi (1936) Larval development and metamorphosis of Argulus japonicus, Memoirs of the College of Science, Kyoto Imperial University, Series B <missing volume>(12): 93-114

U.S. National Museum of Natural History 2002-2021 Invertebrate Zoology Collections Database.

U.S. National Parasite Collection Unit, United States Department of Agriculture 2000 U.S. National Parasite Collection. <missing URL>

Walker, Peter D.; Russon, Iain J.; Haond, Christophe; Van Der Velde, Gerard; Wendelaar-Bonga, Sjoerd E. (2011) Feeding in adult Argulus japonicus Thiele, 1900 (Maxillopoda, Branchiura), an ectoparasite on fish, Crustaceana 84(3): 307-318

Wilson, Charles Branch (1902) North American parasitic copepods of the family Argulida, with a bibliography of the group and a systematic review of all known species, Proceedings of the United States National Museum 25: 635-742

Wilson, Charles Branch (1902) New species of Argulus, with a more complete account of two species already described, Proceedings of the United States National Museum 27(1368): 627-655

Wilson, Charles Branch (1944) Parasitic copepods in the United States National Museum, Proceedings of the United States National Museum 94: 529-582